Making your own lab instruments

[Andrey Mikhalchuk] is trying to gather a base set of lab instruments. Specifically, he’s looking for hardware that will let him quickly filter solids out of a liquid. He first started by adding a cotton disk to a plastic funnel. It does the job, but when left to gravity it’s quite slow. He needed a way to speed up the flow even when the filter is heavily clogged with particulates.

There’s already a solution to this problem. It’s a glass container called a Büchner Flask. These feature a glass tube coming out from the neck. By hooking a vacuum pump up to this tube, reduced pressure inside the flask will pull the liquid through the filter in no time. Rather than purchase the specialty item, [Andrey] altered a rubber stopper to accept both the funnel, and a glass tube. This is a cheaper version because it uses a common conical flask but it works just as well. To create the vacuum, an altered bike pump was used. Check out videos of both hacks after the break.

As a chemist, one of the best ways to make a cheap vaccum is to use running water, using Bernoulli’s principle : add a T to your tap, and run water through the “top” part of the T. A vaccum is going to form at the base, so connect your tube to it. Its a cheap and effective way, although it does waste water.

And the glassware hacks aren’t even all that dated. Sadly, I see even the used copies, only 2 available, are going for USD$50 and up.

I spent many hours with that book in my high school library back in the 1970’s; it was already dated, but the ingenuity and creativity shine through. If Hackaday was a companion site to a major scientific journal, it would be that book.

(In sadder news, SciAm is today a pale shadow of what it was in the days when a book like that could be accumulated from its columns.)

Yeah I agree with localroger When i Was little kid The books even old ones were made so much better older tech but the material was A+++ even popularmechanics was 10 times better 1 time i found an odd shaped book my dad got at a garage sale it was as thick as a big phonebook but the pages were only half the width ( i think it was so you could take it anywhere) and it had every Macgyver hack Known to man for the time,lab,eletronic,build anything,fix almost anything… then years later my buddies brother was taking classes and was going into the FBI and instead of 70’s burnt orange it was black same shape & size but black! It had a strange title to But thats all I remember anybody else remember a book like that?

TheCreator: Great idea! However there is a problem with vacuum cleaner … when the funnel is empty it starts sucking air thru the system and can pick up a drop or two of the product.

Now the question is what are you filtering. If it’s just a dirty water the vacuum cleaner probably will be fine, just smell bad. If it’s ferric chloride (the stuff I built it for) – that’s whole different story and it’s not very long (for the vacuum cleaner).

Pump is safer. It also doesn’t need batteries so you can use it outdoors. And if it will pick up some bad stuff you can always get another one for a few bucks.

As a biochemist, I’ve used Buchner flasks hundreds of times with Buchner funnels. I like this homemade version, although I doubt I would ever use it in the lab :) We have, however, used very similar versions (no filter, just two tubes out the top) to create vacuum traps between the Buchner flask and the vacuum source.

I would suggest cutting off the top half of the filter he’s using, then cut and glue a cylinder in place. Fit a circular disc of plastic with holes ~2-3mm apart at the joint of the cylinder and sloped area (just like how he did it with the plastic milk cap). This will give you a decent Buchner funnel. Being flat, it keeps your product from getting too congested in one area. I would also recommend using filter paper discs cut out of coffee filters if you can’t get any decent qualitative filters. Just make sure that they’re of identical or slightly larger size to the circular disc you made earlier.

Finally, I would recommend using an aspirator on the tap for creating a vacuum. I believe [DdD] mentioned it earlier, although I was unsure as to what exactly he was talking about (aspirators rely on the Venturi effect). I would imagine that they’re cheap (plastic at least), although you can easily build one yourself with parts at the hardware store. These create great vacuum and if you’re worried about wasting water, you can always recycle it. Wash some dishes or something while it’s filtering :)

only problem i see is that if you were going to keep the retentate rather than the filtrate and it was critical for it to dry for 5+minutes with a regular vacuum set up, you’d get tired pumping and probably wouldn’t work as well as if you had a real vacuum

I figured he would use the burner to polish the cit of the glass tubing. I seem to recall that’s how we did it in school. Maybe I missed in the video I expect to see him remove the check in the tire pump. No doubt the scientific America book is out there on the web somewhere, and it looks like some of the material from the book can b for on a CDROM from Scientific American. The book describe as in good condition can be found used as low as $28. This http://www.noah.org/science/x-ray/stong/ is credited to the book.

Working in a “pharma-industry supplier” company, we still sell some of these systems. They are decades-old but very practical when you’re on the field and need to filter water samples for microbial charge evaluation. They don’t need electricity, can be flamed ‘sterilized’ if used in conjunction witha glass or stainless steel funnel and are very resistant to shocks. We even probably have somewhere in an old catalogue small incubators that can run from a car’s battery…

I still have in my little personnal museum a [gorgeous] stainless steel syringe from 1979 with a “T” connection at it’s end which pulls liquid at one end and blows it at the other end, removing the need for a Büchner flask.

One thing worth thinking about is that buchner flasks are (were?) made of thicker glass than plain old conical flasks. Sort of like Champagne bottles being thicker than still wine bottles.

Plainly [Andrey Mikhalchuk] isn’t going to have a problem given his bicycle pump, but would it survive a vacuum pump? I’m thinking of a salvaged pump/compressor assembly from and old fridge or freezer.

I realise that the filter would have to be seriously blocked, plus anyone doing this sort of thing should be both wearing safety gear and paying attention, but in my experience imploding glassware is much the same as exploding glassware, plus not all solvents are benign.

The scientific American book can be found on rapid share. Doesn’t lend itself well for reading using the computer, but 605 pages is a lot to print. You have to rotate some of the page images to read using the computer.http://preview.tinyurl.com/3g67uwx

I like the DIY aspect but, you do have to have a cost/benefit mark to go by. For instance, you can buy a buchner flask, gooch crucible and stopper for less than 20 bucks. Not really worth it IMO but, it is still neat seeing people using their brains.

Pete: Could you please send a link to a $20 set? I was looking for one before building my own but the only one I found was $70 shipped from ebay (including the pump). This setup could be done however with
– Jam jar: free
– water plastic bottle (for the funnel): free
– I found they use nice plastic tubing as a part of helium balloon holder in Party city: free
– bicycle pump: $8 (got mine from Target)
– filters are cotton disks or coffee filters (the latter is in fact better because they are lint-free) or paper towels – basically free

So the total cost of this setup is as little as $8 (for the pump). I only used Erlenmeyer flask, rubber stopper and glass tubing because I had them, all these are replaceable (I added a note about this to the building blog).

I am not suggesting you go out and buy these things however. I was merely stating that everybody has a point where making your own equipment is either too much work or costs too much to make it worthwhile for them. ~$20 seems like a small investment for lab equipment. Who here would spend that same $20 on a “build your own led throwie” kit? No one here I’d bet.

Pete: Thanks for the links! That’s $28 shipped and without the pump, still a great price, better than what I found myself.

I also agree with your point. If fact the idea I had while making the video was telling about different approaches to speed up filtration, not building the lab equipment. Hard to believe, but there are a lot of people out there who do not know about vacuum filtration :)

UNESCO or UNICEF used to have a book for science teachers that illustrated how to make science equipment when teaching in undeveloped countries. I gave mine to a Peace Corps friend and have been trying to find a replacement ever since. Are you familiar with such a resource? If so, please send me an email at: irenebaron@irenebaron.com
Thank you.http://www.irenebaron.com